Hello

very sorry to hear this. As someone living with terminal cancer, aged 56 maybe I can offer you some help? Obviously I see things from the patients perspective, and that could be useful. The main thing I would say is to take the lead from your sister . If she seems to want to talk about certain matters, allow her to do that. Dont try to steer the conversation around to what you think it should be. What type of personality is she? We are all so different. Would she want someone to just listen? To talk through practicalities? To openly talk about the fact that the cancer is stage four or incurable, and the implications of that? 
 

For me, consistency is a big one. Maybe check in with her regularly, once or twice a week? Follow through. Don't offer to call, then forget to do so, or avoid the situation through fear. It's hard on everyone, the patient, and loved ones, but she really needs your help. Generally, advice giving is not welcomed. She will have to make her own decisions about treatment etc. I had people telling me to stay strong, but I felt it as a pressure. It was well meaning but I actually needed to cry, to rage against the injustice of it all, to just be myself and acknowledge the reality of what is happening. 
 

I do want to talk about end of life, not in a morbid way but in a realistic way. But we are not all like that. Some people prefer not to. I get the impression that you are still processing a lot of this yourself. You need help and support also. Some describe cancer as a marathon not a sprint. It's a long haul. Sorry, I don't mean to be negative! Just realistic. It's OK not to know what to say, you are human. Something like' I love you, and I am so sorry you are going through this' is s a good start.

take care, Karen